There are three or four roms based on the latest Android 5.0 preview on XDA, but they don't mean you'll get the OTA update any quicker, or at all, as to install a custom ROM you'd need a custom recovery plus an unlocked bootloader and therefore wouldn't be able to download or use the official OTA. You need to either remain on (or return to) stock and wait for the notification, or wait for a dev to make a flashable custom rom of the final release.